As questions arise, collect them here. Do your best to identify who the best person to answer is. Add new questions to the top of the page. From Hannah: Mary and I went out to the wetland plot (105), and it was most certainly a wetland! I have a picture on my phone which I can show you in class, but it is full of water, only accessible by canoe/kayak, ducks and geese swimming around. From the GPS/aerial, we could see where the plot was, and there were 5 or 6 dead trees (standing) in the water.
Where should we go/what should we do from there?
Questions for David Nowak's visit
What is the best way to handle DBH for crabapple trees which have several large branches instead of a central trunk? If there is a single trunk emerging from the ground, measure it and record the height of measurement. Otherwise, treat as multiple boles on a single tree. <answer by george>
How does the model use DBH at 1 foot above ground vs. 4.5 feet?
How do we deal with privette? Because we are not doing shrubs, we are technically to treat this as a tree, but there are so many stems that it would take hours to measure. Can we ignore and document this choice? What issues are associated with that bias? Count the number of stems in groups of 1" stems, 2" stems, etc and write down. Measure the area occupied by the privette. When entering the data, add up the basal area of all the stems and enter it as a single stem.
Should we use a higher diameter threshold, say 2" or 3" instead of 1"? This could save us significant time in the field. Discuss tradeoffs. (This might "solve" the privette issue.) No - too much information lost.
How do we handle dangerous plots (ie, on RR tracks, major highways, etc)? Just dropping them would lead to some bias. So far, George and Evan (instructor and TA) have been doing these, but there are a couple that even they are balking at. Just drop them.
Is it possible for multiple people to enter data and then combine, or does it all have to be done by one person, or at least on a single dataset? Someone needs to call iTrees help and ask about this.
What do we enter for % missing and % dieback - we're thinking zero. Go with 5% and be sure to document.
We have discontinued collecting distance and direction to each tree because (1) we do not plan on revisiting (which is what the manual says these are for) and (2) it takes to long. However, we have discovered that the software requires that we enter values. Can we just enter 0, 0 for all? Or do they each have to be different? Try that - of that fails, try 1, 1. Not sure if they all have to be different. If they do, go for something like (0,1) (0,2) (0,3) which makes it obvious that these are not real measures.
Better use of time than going to Raleigh Parks meeting?
I (george) have been thinking about the Raleigh Parks meeting and wonder if it's really worth almost an entire lab period for the entire class to go. I think you might learn from it, but I'm not sure it's the best use of our time. I offer you the opportunity to propose a better use of your time. I am willing to just go by myself, and I'd also be happy to take a subset of really interested students (possibly those in policy) rather than the whole class.
Please propose alternatives here.
One I (george) can think of is a GIS team locating property owner information, and another team starting to call them / write letters / etc.
Those who stay behind could learn GPS and then teach the rest. This would work especially well if one person from each team stayed behind.
I agree with george UFORE questions for David Nowak.
1. Can we change the minimum dbh criterion to 4" instead of 1"? What would be lost by doing so?
Yes - you can change the minimum dbh. What is lost is an accounting of trees less than 4" and their effects. My guess is that the total urban forest tree count will drop by about 20-30% without the trees <4", but the effects will not drop by the same percent (as these are the smallest trees). Leaf area index will also drop, which will reduce pollution removal estimates. However, your total tree cover percent will likely be for all trees on the plot, thus there will be a slight mismatch there (only trees >4" measured, but canopy cover measured for all trees). This should not be a major issue if explained to the reader. The main issue is that you will not be accounting for the effect of all the trees in the area (which is OK if that is what you want and are clear to the reader on what you did). Advantage is that it will reduce your field work load.
2. Is it reasonable to do the following:
Break Raleigh into districts (say 8-10)
Pilot the process this semester by sampling only within one or two districts with 50-60 plots
Collect data in the other districts in the fall or next spring
Ultimately combine the data from all districts for a city-wide estimate
Yes - this process could work. The only issue is there would be a time lag among the districts when compiling the total estimate, but this can be explained to the reader. As long as the time lag is not too great, this should not be a huge issue.
3. It's not clear how we should deal with crown die-back in the winter.
You will have to assume some average for all trees. You do not know the dieback, so record the same dieback for all trees based on what you think the average dieback is. What is more important for the analysis percent canopy missing, which is a combination of dieback and pruning and other factors that will reduce leaf area. For this measure you will just have to look at crown shape to deduce the missing canopy. I would just assume either no dieback for all trees or 5% dieback and just realize the assumptions you have made when it come to reporting the data.
4. Do you usually use densiometers for canopy cover on the plot? I don't see a procedure in the field manual for that measure. I would normally go to plot center, take densiometer readings in each of the four cardinal directions, and average them for a plot reading.
We have used densiometers in test cases, but our procedure with the densiometer was too time consuming. You can use a densiometer. We typically use a cover template guide (we can send you one as I see one is not in the manual, but we will now be adding this template to the manual) and then both crew members use the guide to come to consensus on the actual tree cover. Overall this procedure can work well as we have conducted tests against air photo interpretation and the crew results can out close (within 5%) to the photo interpretation. The results will depend upon the crew.
Can we tell property owners that we are working in collaboration with Raleigh Parks and Division of Forest Resources? Do we need permission from those organizations to say that? (Sally and Leslie)
Leslie has given permission to do this with respect to DFR (24 Jan).
We do not have permission from Raleigh yet, and the 30 Jan meeting has been postponed.
Revisiting study area
On 16 Jan we decided to do the whole city, a decision that was based in part on my ability to get reimbursement for your travel mileage. Because of the rules around here, I cannot get mileage for undergraduate students. So, my question to you is "Do you still want to do the whole city, or should we focus on a district closer to campus to save fuel?" Please discuss below - you don't have to initial your comments if you don't want to, but you should probably learn not to hide from your thoughts and opinions.
22 Jan - Class decided to stick with full city. We will find ways to make the travel equitable, and to help anyone who simply cannot afford to drive to Raleigh's hinterlands.
As questions arise, collect them here. Do your best to identify who the best person to answer is. Add new questions to the top of the page.
From Hannah: Mary and I went out to the wetland plot (105), and it was most certainly a wetland! I have a picture on my phone which I can show you in class, but it is full of water, only accessible by canoe/kayak, ducks and geese swimming around. From the GPS/aerial, we could see where the plot was, and there were 5 or 6 dead trees (standing) in the water.
Where should we go/what should we do from there?
Questions for David Nowak's visit
What is the best way to handle DBH for crabapple trees which have several large branches instead of a central trunk?
If there is a single trunk emerging from the ground, measure it and record the height of measurement. Otherwise, treat as multiple boles on a single tree. <answer by george>
How does the model use DBH at 1 foot above ground vs. 4.5 feet?
How do we deal with privette? Because we are not doing shrubs, we are technically to treat this as a tree, but there are so many stems that it would take hours to measure. Can we ignore and document this choice? What issues are associated with that bias?
Count the number of stems in groups of 1" stems, 2" stems, etc and write down. Measure the area occupied by the privette. When entering the data, add up the basal area of all the stems and enter it as a single stem.
Should we use a higher diameter threshold, say 2" or 3" instead of 1"? This could save us significant time in the field. Discuss tradeoffs. (This might "solve" the privette issue.)
No - too much information lost.
How do we handle dangerous plots (ie, on RR tracks, major highways, etc)? Just dropping them would lead to some bias. So far, George and Evan (instructor and TA) have been doing these, but there are a couple that even they are balking at.
Just drop them.
Is it possible for multiple people to enter data and then combine, or does it all have to be done by one person, or at least on a single dataset?
Someone needs to call iTrees help and ask about this.
What do we enter for % missing and % dieback - we're thinking zero.
Go with 5% and be sure to document.
We have discontinued collecting distance and direction to each tree because (1) we do not plan on revisiting (which is what the manual says these are for) and (2) it takes to long. However, we have discovered that the software requires that we enter values. Can we just enter 0, 0 for all? Or do they each have to be different?
Try that - of that fails, try 1, 1. Not sure if they all have to be different. If they do, go for something like (0,1) (0,2) (0,3) which makes it obvious that these are not real measures.
Better use of time than going to Raleigh Parks meeting?
I (george) have been thinking about the Raleigh Parks meeting and wonder if it's really worth almost an entire lab period for the entire class to go. I think you might learn from it, but I'm not sure it's the best use of our time. I offer you the opportunity to propose a better use of your time. I am willing to just go by myself, and I'd also be happy to take a subset of really interested students (possibly those in policy) rather than the whole class.
Please propose alternatives here.
One I (george) can think of is a GIS team locating property owner information, and another team starting to call them / write letters / etc.
Those who stay behind could learn GPS and then teach the rest. This would work especially well if one person from each team stayed behind.
I agree with george
UFORE questions for David Nowak.
1. Can we change the minimum dbh criterion to 4" instead of 1"? What would be lost by doing so?
Yes - you can change the minimum dbh. What is lost is an accounting of trees less than 4" and their effects. My guess is that the total urban forest tree count will drop by about 20-30% without the trees <4", but the effects will not drop by the same percent (as these are the smallest trees). Leaf area index will also drop, which will reduce pollution removal estimates. However, your total tree cover percent will likely be for all trees on the plot, thus there will be a slight mismatch there (only trees >4" measured, but canopy cover measured for all trees). This should not be a major issue if explained to the reader. The main issue is that you will not be accounting for the effect of all the trees in the area (which is OK if that is what you want and are clear to the reader on what you did). Advantage is that it will reduce your field work load.
2. Is it reasonable to do the following:
Yes - this process could work. The only issue is there would be a time lag among the districts when compiling the total estimate, but this can be explained to the reader. As long as the time lag is not too great, this should not be a huge issue.
3. It's not clear how we should deal with crown die-back in the winter.
You will have to assume some average for all trees. You do not know the dieback, so record the same dieback for all trees based on what you think the average dieback is. What is more important for the analysis percent canopy missing, which is a combination of dieback and pruning and other factors that will reduce leaf area. For this measure you will just have to look at crown shape to deduce the missing canopy. I would just assume either no dieback for all trees or 5% dieback and just realize the assumptions you have made when it come to reporting the data.
4. Do you usually use densiometers for canopy cover on the plot? I don't see a procedure in the field manual for that measure. I would normally go to plot center, take densiometer readings in each of the four cardinal directions, and average them for a plot reading.
We have used densiometers in test cases, but our procedure with the densiometer was too time consuming. You can use a densiometer. We typically use a cover template guide (we can send you one as I see one is not in the manual, but we will now be adding this template to the manual) and then both crew members use the guide to come to consensus on the actual tree cover. Overall this procedure can work well as we have conducted tests against air photo interpretation and the crew results can out close (within 5%) to the photo interpretation. The results will depend upon the crew.
Can we tell property owners that we are working in collaboration with Raleigh Parks and Division of Forest Resources? Do we need permission from those organizations to say that? (Sally and Leslie)
Leslie has given permission to do this with respect to DFR (24 Jan).
We do not have permission from Raleigh yet, and the 30 Jan meeting has been postponed.
Revisiting study area
On 16 Jan we decided to do the whole city, a decision that was based in part on my ability to get reimbursement for your travel mileage. Because of the rules around here, I cannot get mileage for undergraduate students. So, my question to you is "Do you still want to do the whole city, or should we focus on a district closer to campus to save fuel?" Please discuss below - you don't have to initial your comments if you don't want to, but you should probably learn not to hide from your thoughts and opinions.
22 Jan - Class decided to stick with full city. We will find ways to make the travel equitable, and to help anyone who simply cannot afford to drive to Raleigh's hinterlands.